With the renewed interest in land-based transportation around the world, magnetic levitation (MAGLEV) vehicles are being increasingly suggested as new transportation alternatives. In a MAGLEV system, people and freight are transported for relatively long distances (100 to 1,000 km) at high speeds (135 m/s) in aerodynamically streamlined vehicles or trains suspended by magnetic forces. While the high-speed frictionless (except for air friction) operation of such trains makes them attractive, it also presents difficult challenges for the development of a suitable propulsion and power transfer systems. Linear electric motors offer the best alternative for propelling and powering such MAGLEV vehicles.
A linear sychronous motor (LSM) has a drive coil assembly or stator having a plurality of coils or windings and one or more magnet assemblies or rotors including a plurality of magnets. Propulsion or braking electromotive force (EMF) is produced by leading and trailing sides of the coils being cut by the flux lines of the magnetic fields of the magnet according to Faraday+s law. The sides of traditional coils are shaped to be cut by the flux of two opposite magnetic poles at a time, thus doubling the power output. Power and control drive electronics also are necessary to monitor the electrical power to and from the motor.
When using a LSM to propel a vehicle, multiphase electric power can be supplied in either of two ways: to coils on a guideway that defines the path of the vehicle or to coils on the vehicle. A guideway or track with powered coils (windings) is called "active guideway," "long primary" or "long stator." A system with active coils on the vehicle is called "active vehicle" or "short primary." The unpowered section of an LSM is called the field. In an active guideway LSM the current in the coils is controlled by power and control circuitry so as to create a traveling magnetic field that moves with the MAGLEV vehicle. From this synchronous movement comes the term synchronous motor.
A main obstacle for the commercial implementation of MAGLEV vehicles is cost. Given the extended distances over which a MAGLEV vehicle must travel, the cost for components for most linear motor systems is exorbitant. New linear motors that exhibit the desired power output and control, but use either existent components more efficiently or more cost efficient components are necessary. Even a relatively small savings per unit length of track will result in significant savings over a several hundred-kilometer train route.